Q.: We've had some tilt-up panels stick to the floor they were cast on and have had a lot of trouble breaking them loose. This trouble happened with panels cast on a floor that had been built on a hot, very breezy day. It has been suggested to us that rapid drying from the fresh concrete surface could later have caused the curing agent-bondbreaker to be less effective. Is this possible? Is there a remedy?
A.: If the surface was beginning to dry before the curing agent-bondbreaker was applied, the material could have been drawn into the concrete pores instead of remaining on top. Under such conditions it would be a good idea to apply mist over the floor slab, using a fog nozzle, to fill the concrete pores before the curing and bondbreaking agent is applied. It could also help to apply a second bondbreaking coat at right angles to the first, but if so this must be done before any of the reinforcing steel for the tilt-up panel is in place. Otherwise it could interfere with bond of the steel to the concrete.